1. Field of the Invention
The present invention relates to a switching device for a plasma display panel (PDP). More specifically, the present invention relates to a PDP switching device that facilitates operation at a high voltage.
2. Discussion of the Related Art
Various flat panel displays such as the liquid crystal display (LCD), the field emission display (FED), and PDP have been developed. Of these, the PDP has higher resolution, a higher rate of emission efficiency, and a wider view angle. Accordingly, the PDP is in the spotlight as a substitute display for the conventional cathode ray tube (CRT), especially in the large-sized displays of greater than forty inches.
The PDP shows characters or images using plasma generated by gas discharge, and it may include more than hundreds of thousands to millions of pixels arranged in a matrix. The PDP is divided into a direct current (DC) PDP and an alternating current (AC) PDP according to an applied driving voltage waveform and discharge cell structure.
FIG. 1 shows a partial perspective view of an AC PDP.
As shown in FIG. 1, scan electrodes 4 and sustain electrodes 5 are formed in parallel pairs on a first glass substrate 1, and they are covered with a dielectric layer 2 and a protection film 3. A plurality of address electrodes 8 is formed on a second glass substrate 6, and the address electrodes 8 are covered with an insulator layer 7. Barrier ribs 9 are formed between and in parallel with the address electrodes 8 on the insulator layer 7, and phosphors 10 are formed on the surface of the insulator layer 7 and on both sides of the barrier ribs 9. The first and second glass substrates 1 and 6 are sealed together to form a discharge spaces 11 therebetween so that the scan electrodes 4 and the sustain electrodes 5 are orthogonal to the address electrodes 8. A portion of the discharge space 11 at an intersection of an address electrode 8 and a pair of the scan electrode 4 and the sustain electrode 5 forms a discharge cell 12.
FIG. 2 schematically shows a typical electrode arrangement of the AC PDP.
As shown in FIG. 2, the electrodes comprise an m x n matrix. The address electrodes A1 to Am are arranged in the column direction and the scan electrodes Y1 to Yn and the sustain electrodes X1 to Xn are alternately arranged in the row direction. The discharge cell 12 corresponds to the discharge cell 12 in FIG. 1.
A conventional method for driving the AC PDP comprises a reset period, an address period, and a sustain period.
In the reset period, cells are initialized for proper addressing. In the address period, an address voltage is applied to cells (addressed cells) that are to be turned on, which accumulates wall charges in those addressed cells. In the sustain period, sustain discharges occur in the addressed cells to display images on the PDP.
With this method, a desired voltage may be applied by a plurality of switching devices in the reset, address, and sustain periods. But due to an applied pulse-type voltage, a narrow, pulse-type current may flow rapidly through the switching device in the address period and the sustain period. A Metal-Oxide Semiconductor Field Effect Transistor (MOSFET), which has a fast switching speed, is usually used for a switching device. However, the resistance Ron between the MOSFET's drain and source when it is turned on may increase sharply when a withstand voltage of the MOSFET increases. Therefore, as the pulse type of current flows, a value of a Root-Mean-Square (RMS) may be very high for the MOSFET. Accordingly, a MOSFET may have a high conduction loss and it may generate a lot of heat.
A method for switching by using a plurality of MOSFETs M1 and M2 coupled in parallel, as shown in FIG. 3, may be used for solving this problem. However, it may be advantageous to increase a partial pressure of Xe gas input into the PDP, which requires more MOSFETs coupled in parallel since a higher driving voltage is necessary due to the increased partial pressure. But increasing the number of MOSFETs may increase cost, the size of a driving board, and the number of driving circuits.